The invention operates in the general environment of display brightness adjustment. When a shaft of light is cast across a screen, it can cause reduced viewing quality in an area whilst leaving other parts of the display unaffected. When viewing quality is important, a user will attempt to block out a light source casting glare or unwanted shafts of light onto screen. Normally darkening the environment works but this is not always possible.
The effects of bright light on a screen can be attenuated by raising the brightness. Most devices with screens (for example, a television or a monitor) only allow the whole screen to be brightened or dimmed; adjusting to optimize affected areas can lead to the unaffected areas looking worse.
A known solution automatically adjusts brightness by light-sensors built into a device. Mobile phones often make use of this, detecting the lighting levels of their surroundings and dimming or brightening the screen accordingly. The drawback of this method is that the sensor only detects overall ambient light level, and as such the whole screen is adjusted in accordance with the measured ambient light level. This solution also suffers the same drawback as manual brightness adjustment in that brightness is adjusted for the whole screen.